1. Field of the Invention
The present invention relates to a built-in antenna apparatus for a portable terminal. More particularly, the present invention relates to a portable terminal with a built-in antenna having a Global Positioning System (GPS) capable of increasing an upper hemisphere radiation to improve the reception.
2. Description of the Related Art
Recently, an antenna of a portable terminal is changing from an externally protruding helical antenna (or whip antenna) to a built-in antenna that is equipped internally in the terminal. This is because the externally protruding antenna apparatus is not esthetic and susceptible to damages caused by frequent impacts.
In a typical built-in antenna apparatus, there is an antenna radiator having a specific pattern and mounted on a main board of the terminal. Just about all manufacturers of the terminal are competing to improve radiation performance while focusing on a slimmer, thinner, and lighter terminal.
The aforementioned built-in antenna apparatus is classified according to the frequency band used by the terminal. Examples of the antenna include a monopole antenna, a Planar Inverted F Antenna (PIFA), etc.
The monopole antenna has only a feeding portion for supplying power to a signal line of a main board. The PIFA has the same arrangement but also has a ground portion that is grounded to a ground member of the main board. The PIFA is more widely used and may also be used by forming a Dual Terminal Antenna (DTA) type pattern depending on various bands used by the terminal.
The PIFA improves a Specific Absorption Rate (SAR) property by attenuating a beam directed towards a ground surface which is re-extracted and directed towards a human body. Further, the PIFA has a directivity property that enforces a beam extracted towards the radiation portion. Moreover, the PIFA operates as a micro strip antenna in which a length of a plate-type radiation portion is decreased. Therefore, there is an advantage in that a low profile structure can be realized.
Meanwhile, in recent years, a Global Positioning System (GPS) is readily provided in a terminal, and thus the terminal must be equipped with an antenna radiator for the GPS application. The GPS antenna radiator may be formed integrally when forming a main antenna radiator for communication. The GPS antenna radiator is generally mounted on a main board of the terminal independently from the main antenna radiator. In general, a PIFA type GPS antenna radiator or a chip antenna radiator is mounted.
However, the aforementioned conventional antenna radiator type is dependent on a surrounding ground (i.e., a ground member), thus an electric field direction of the radiator is directed towards the ground. As the electric field direction of the terminal is directed upwards more in operation, the conventional GPS antenna radiator fails to perform efficiently. A chip antenna, which shows relatively high efficiency, can be used but not economical.